Hp500efi rebuild
 

I recently bought a hp500efi and looking to build a 650 hp 540ci out of it. I'm curious what other guys are running. Retuning the efi system, carb, or installing aftermarket efi system such as holley. As always I appreciate all the help I can get.

Stock EFI intake hits a wall around 600-620hp

These 540's made 630hp, thats all the intake will support

https://cimg2.ibsrv.net/gimg/www.off...0c928d25fd.jpg

I'm assuming bigger injectors? Any idea what I would need to use if I decide to use the efi

This can be done for 13K, looks like more power available with added services.


https://cimg4.ibsrv.net/gimg/www.off...9ffc5a0ae1.png

65 lb hour injectors, stock TB and intake runners, custom grind double swap cam and AFR heads

a 525 style flame arrestor with a monoblade tb properly tuned will help a built 500 gain about 15 to 20 hp on top and more peak torque. The FA's are super expensive at 765$ each though. You CAN buy the 525 throttle blades for 50$ to bore out IF you know a competent machinist . hardin or somone sells a 525 fa for 600$

Did you have the FA's on when you dynoed? I saw a restriction from them at less hp on my dyno

yes, full dressed with CMI sweepers, maybe we should of taken them off and do a pull, but we didnt

I honestly thought someone would have suggested selling the HP 500 and just buying a 540 as opposed to conversion.

A lot less work and prob cost less in the long run too.

https://www.ebay.com/itm/MerCruiser-...QAAOSwjL5ZFdX3

https://www.ebay.com/itm/540-Bulldog...IAAOSwnK9ZVqxK

https://cleveland.craigslist.org/bpd...145891904.html

Just curious, what did you buy the 500 HP for? I've got a 502 MAG (black engine) that I would ultimately like to upgrade and a 500 HP EFI would be what I'd want or replicate for reliability.

It came with the boat. That's why I'm unsure what route I'm taking. I think I'm just building a carb 540 and selling what I dont use

ebay? thats a risk. the "540 bulldogs" are not bulldogs from mercury, not even the correct stroke. bulldogs had lunati cranks and manley rods too.

find a good local builder, not ebay.

that's my plan I have a good guy that I worked with before and he is pushing me into a carb

Your 500efi is worth more complete. You'd be better off to sell it complete if you build a 540 carb engine

Agree!

I was just using the links to show approximate cost of a 540 engine already to go. Someone posted a link for a $13k conversion to the 500 engine.

So I was just showing that you could sell the 500 HP EFI and buy a 540 for maybe half price.

my hp 500 efi has a broke crank and 2 damaged pistons needs some other stuff accessory wise but I was thinking of throwing a crank and a few pistons in it and offloading it just wasn't sure what it would be worth without the headers and accessories

along with that I just bought the boat with the engine already out and torn down

you sure the blocks not damaged ? where did the crank break, very odd I dont think Ive ever heard of a 500 efi breaking a crank, did it hydraulic a cylinder

not 100 percent I'm going the have the machine shop check it out but it looks ok to my eye

i bought two core REAL bulldog shortblocks for 3k. tall deck bowties, lunati cranks, and manley rods. built two very mild 557 cid engines with all top quality parts. 1050 quick fuel carbs. run great, no loading up, start with one pump of the throttle every time.

Were you there when they were dynoed, did you get to see the map/kpa readings at wot at all? when I tested them on a 540 w all out modded 500 intake it killed 20+ hp, wot map went from 98.5 to sub 95 with and without

I was there actually hooked them up on the dyno carts for Brad, hp and tq was all I was concerned with, his accident happened before I got the print outs. RIP